SQL Server :: Working With Geometry Data Type - Error: "Msg 403 - Level 16 - State"

I have a sql server 2008 database table that has a column of type geometry. I am trying to update the data for a record. The data that needs to be inserted into the database is a POINT location that i get off of two text fields on an .NET form. I pass the values into a procedure to update the record. Below is what I have been trying with no luck. The @lat and @long variables I pass into the procedure as type. Does anyone have a good way to update this data? When I try to compile this code it gives the error: "Msg 403, Level 16, State 1, Procedure UPDATE_LAT_LONG, Line 19 Invalid operator for data type. Operator equals add, type equals geometry."

create
PROCEDURE [dbo].[UPDATE_LAT_LONG]
(@PK int,
@lat geometry,
@long geometry )
AS
BEGIN
SET
NOCOUNT
ON;
UPDATE MITIGATION_REPORTING.dbo.MR_MITIGATION
SET MR_MITIGATION_LATITUDE_LONGITUDE =
'(''POINT('+cast(@lat
as
geometry)+' '+cast(@long
as
geometry)+')'')'
WHERE MR_MITIGATION_PK = @PK;
END